<!DOCTYPE html>
<style>
  /* In border-collapse mode, inset becomes ridge. */
  table { border-collapse: collapse; border-spacing: 0 }
  table, td { border-style: inset; }
  td { border-width: 20px; width: 100px; height: 100px}
</style>
<table>
  <tr>
    <td></td>
  </tr>
</table>
